The invention relates to compounds of the formula I, to a liquid-crystalline medium which comprises at least one compound of the formula I, in which R1, R1*, L1, L2, L3 and L4 have the meanings indicated herein, and to the use thereof for an active-matrix display, in particular based on the VA, PSA, PS-VA, PM-VA, PALC, IPS, PS-IPS, SA-VA, SS-VA, FFS or PS-FFS effect.